Palomydes shows up and again Tristram fights him. Then all goes well for a time, until Andret, Tristram's cousin, jealous of Tristram's glory, shows King Mark that Tristram is talking with Isode at her window. Mark attacks, Tristram ludicrously overcomes and humiliates him — chasing the king and slapping him with the flat of his sword until the king falls on his nose. Afterward, Mark's advisers recommend that he make peace with Tristram, the best of his protectors, and Mark gloomily does so.
But Tristram's troubles are by no means over. Lamerok of Wales, partly to get revenge on Tristram for shaming him once, and partly to divert to Mark's court troubles that must otherwise come to Arthur's, sends King Mark a magical cup which can reveal whether women are loyal. When Isode fails the test, Mark's advisers tell him not to trust a mere sorcerer's cup.
Andret then lies in wait with twelve knights in Isode's bedroom and, when Tristram lies down naked beside her, leaps out and seizes him, binds him, and takes him to the king. Tristram reminds the court of all he had done for Cornwall, but Andret scoffs and prepares to kill him on the spot. Tristram breaks free, kills Andret, and escapes. After this Tristram and Isode live happily for a time in a forest hut, but at last Mark gets Isode back and imprisons her.
Tristram, again suffering a wound that will not heal — and now unable to get to Isode for help — is forced to go to Britain, to another lady, Isode le Blaunche Maynes. Time passes and at last Tristram marries the new Isode but will not consummate the marriage. He hears now that Launcelot scorns him for his falsehood to his lady. Guinevere meanwhile writes letters of comfort to La Beal Isode.
